Filter element and fuel filter

ABSTRACT

The invention concerns a filter element ( 1 ), in particular of a fuel filter for motor vehicles. The filter element ( 1 ) is received in a filter housing ( 2 ) and comprises a filter body ( 3 ) with a filter material ( 5 ) that is arranged in folds ( 4 ). Between two folds ( 4 ) a heating element ( 6 ) for the fuel is arranged.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.12/671,027, now U.S. Pat. No. 8,535,519, the entire disclosure of whichis incorporated herein by reference. U.S. patent application Ser. No.12/671,027 is a U.S. National Stage Entry under 35 USC 371 ofinternational application PCT/EP2008/059563 filed Jul. 22, 2008 whichclaims priority to German patent application DE 20 2007 010 603.3 filedJul. 27, 2007.

TECHNICAL FIELD

The invention concerns a filter element, in particular of a fuel filterfor motor vehicles as well as a fuel filter.

PRIOR ART

The flowability of fuel decreases with dropping temperatures.Particularly diesel fuel has a tendency to gel at wintery temperatureswhich leads to disruptions of the fuel supply of the vehicle motor. Thegelled fuel in particular clogs the fuel filter that is arranged in thelow-pressure circuit of the fuel supply so that its flow resistanceincreases excessively. The drive motor cannot be supplied with therequired flow rate of the fuel. A complete interruption of the fuel flowis possible.

To avoid the aforementioned disadvantages, heated fuel filters are used,in particular for diesel vehicles. In known constructions the filterhousing has an integrated electrical heater that heats the fuel flowingthrough and in this way generates the desired low viscosity of the fuel.The manufacture of such a filter housing is complex and cost-intensive.A significant portion of the generated heat output is used for heatingthe fuel filter and its housing. Only a portion of the heat output isavailable for the desired heating of the fuel. The fuel stream that isflowing through only contacts proportionally the heated housing walls sothat a non-uniform heating occurs.

The invention has the object to further develop a filter element of theaforementioned kind in such a way that its efficiency is improved.

The invention has moreover the object to further develop a fuel filterof the aforementioned kind such that, without impairment of operationalsafety, a more compact construction is achievable.

The above objects are solved by a filter element and a fuel filter aspresented in the claims.

SUMMARY OF THE INVENTION

A filter element, in particular of a fuel filter for motor vehicles, isproposed that is provided for use in a filter housing. The filterelement comprises a filter body with a filter material that is arrangedin folds. Between two folds of the filter material a heating element forthe fuel is arranged. The heating element in this connection isadvantageously arranged on a raw side of the filter body. Thearrangement according to the invention of the heater element between twofolds requires neither additional space in the filter element nor in thefilter housing. The heating element that is especially an electric oneis positioned directly within the fuel flow so that an immediate andtherefore loss-free heat transfer is achievable. With a compactconstruction and minimal heating power the flowability of the fuel flowcan be maintained. The arrangement of the heating element at the rawside prevents reliably clogging of the filter material. The heatingelement that is in particular fixedly connected to the filter body isexchanged together with the filter body in accordance with theprescribed servicing intervals so that age-related functional failuresof the heating element are prevented. As a whole, the efficiency of thefilter element is improved and thus a reliable, operationally safe fuelsupply of the drive motor is ensured.

The fuel filter according to the invention, in particular for motorvehicles, comprises a filter housing and the aforementioned filterelement. In this connection, the filter element has a terminal diskwhich may include a circumferentially extending seal for sealingrelative to the filter housing. Between the terminal disk and a lid partof the filter housing a supply chamber is formed into which opens asupply line. The terminal disk has a through opening that adjoins theheating element. Advantageously, the through opening is provided with ahydrodynamic conducting body. The terminal disk with the seal arrangedthereat generates together with the lid part of the filter housing asupply chamber that as a whole is fluid-tight and through which theincoming fuel is supplied to the through opening. In particular with theaction of the hydrodynamic conducting body, the fuel flow is guidedthrough the through opening directly to the heating element. The fuelflow is heated as a whole and homogeneously to the desired degree beforeit flows from the raw side through the filter material to the cleanside. The formation of local sites where fuel is heated unsatisfactorilyis avoided.

In an advantageous further embodiment the heating element is sealedrelative to the lid part with a seal wherein the lid part has a contactopening for electric connecting contacts of the heating element,reliably separating the fuel flow from the electric connecting contacts.In case of servicing work, electrical plugs can be removed easily fromthe connecting contacts and can be pushed on again without having totake care of fuel seal-tightness. The servicing work that has to becarried out in this connection can be performed easily while any faultyoperation is avoided.

The heating element has advantageously a differential pressure sensorfor detecting a differential pressure between the raw side and the cleanside of the filter body. In particular, the differential pressure sensoris provided for controlling an electric fuel pump in the low-pressurecircuit of the fuel supply and/or for controlling the heating power ofthe heating element. The differential pressure between raw side andclean side that is generated as a result of the flow resistance of thefilter element is utilized as a measure for the fuel viscosity thatchanges with temperature. When the determined differential pressureincreases undesirably as a result of fuel that is too cold and thereforetoo viscous, alternatively or in combination the conveying output of theelectric fuel pump and/or the heating power of the heating element canbe increased. As an alternative to the governing action, it may also beexpedient to employ a threshold control or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

One exemplary embodiment of the invention will be explained in thefollowing with the aid of the drawing in more detail. The only FIGUREshows in a partially sectioned illustration a diesel fuel filter with afilter element embodied in accordance with the invention with anintegrated fuel heater.

EMBODIMENT OF THE INVENTION

The only FIGURE shows in a partially sectioned illustration of oneexemplary embodiment of a fuel filter 10 for diesel fuel for a motorvehicle that is embodied in accordance with the present invention. Otherapplications and in particular other fuel types can be envisioned also.The fuel filter 10 comprises a filter housing 2 that is closed off by alid part 13 that may be detachable. In the filter housing 2 a filterelement 1 is secured which may be removed in predetermined servicingintervals after detachment of the lid part 13 and is replaced with a newfilter element 1.

The filter element 1 comprises a filter body 3 with a filter material 5that is arranged in folds 4. As filter material 5 filter paper isprovided. However, other filter materials 5 may be expedient also. Theextension of the folds 4 is indicated by dashed lines 26. The filterhousing 2 and the filter body 3 are substantially embodied to becylindrical wherein the folds 4 extend in radial direction and parallelto the longitudinal axis of the cylindrical filter element 1 or thecylindrical filter housing 2. External to the filter material 5 inradial direction there is the raw side 7 of the filter element 1. In theradial inner area an approximately cylindrical cavity is provided thatforms the clean side 8 of the filter element 1. In operation, the filtermaterial 5 is flown through radially from the outer raw side 7 to theinner clean side 8. When doing so, a differential pressure between theraw side 7 and the clean side 8 is generated that acts inwardly in theradial direction on the filter material 5. For supporting the filtermaterial 5 relative to this differential pressure, a support grid 24 isarranged inwardly in radial direction.

At both end faces, the filter body 3 has a terminal disk 11, 22,respectively. In the illustrated embodiment the terminal disk isprovided with edges seals 12, 23 that extend circumferentially about thecircumference in the form of elastic sealing lips. The seal 12 arrangedin the area of the lid part 13 seals the terminal disk 11 relative tothe filter housing 2 as well as relative to the lid part 13. The seal 23of the axially oppositely positioned terminal disk 22 is restingseal-tightly against the inner circumferential surface of the filterhousing 2. In the terminal disk 11 that is facing the lid part 13 athrough opening 16 is integrally formed. The two terminal disks 11, 22with their sealing lips 12, 23, the circumferential wall of the filterhousing 2, and the filter body 3 delimit a closed annular space at theraw side 7 of the filter element 1 whose only access is the throughopening 16.

As a result there is also a closed supply chamber 14 formed between theterminal disk 11 and the lid part 13 into which a supply opening 15opens. Into this supply chamber 14 fuel is introduced through the supplyline 15. The fuel flows in accordance with arrow 25 through the supplychamber 14 to the through opening 16 and through it into the aforedescribed annular space of the raw side 7. From here the fuel flow isguided radially from the exterior to the interior through the filtermaterial 5 into the radially inwardly positioned space that defines theclean side 8 from where the fuel flows out through a central outlet line20 of the lid part 13. For separating the supply chamber 14 from theoutlet line 20, a seal 21 is arranged between the terminal disk 11 andthe lid part 13 and extends circumferentially about the mouth of theoutlet line 20.

Between two folds 4 of the filter material 5 an electric heating element6 for the fuel is arranged. For this purpose, the two neighboring folds4 are spread apart in the circumferential direction in order to providesufficient space for the heating elements 6. The heating element 6 ispositioned relative to the circumferential contour of the filter body 3inwardly displaced in the radial direction and is fixedly connected tothe filter element 1. At the predetermined servicing intervals anexchange of the filter body 3 together with the heating element 6 isprovided.

The heating element 6 extends parallel to the axis of the filter body 3between its two terminal disks 11, 22. A contact opening 18 is formedintegrally in the lid part 13 and the adjoining terminal disk 11 whichcontact opening enables an electric plug connection with electricalconnecting contacts of the heating element 6 and a differential pressuresensor 9 to be described infra. The heating element 6 is sealed relativeto the lid part 13 and the terminal disk 11 with a seal 19circumferentially surrounding the contact opening 18. In this way, theelectric connecting contacts are kept away from the fuel flow.

The through opening 16 of the terminal disk 11 that is seal-tightlyclosed off relative to the contact opening 18 adjoins the correlated endface of the heating element 6; the hydrodynamic conducting body 17integrally formed in the terminal disk 11 ensures a controlled flow ofthe fuel introduced through the through opening 16 toward the heatingelement 6. The fuel flow is guided approximately axis-parallel along theheating element 6 and is heated thereby. Subsequently, it is distributedin the afore described annular space of the raw side 7 before it passesin the radial direction inwardly through the filter material 5 to theclean side 8. In an exemplary fashion, a single heating element 6 isshown between two folds 4 with a correlated through opening 16. However,it may also be expedient to provide two or more heating elements 6 witha corresponding number of through openings 16.

The heating element 6 is also provided with a schematically indicateddifferential pressure sensor 9 which is provided for detecting adifferential pressure between the raw side 7 and the clean side 8 of thefilter body 3. The differential pressure of the fuel flow that isgenerated upon passing through the filter element 1 from the raw side 7to the clean side 8 is determined by the differential pressure sensor 9and is used by a non-illustrated control or governing unit as a measurefor the viscosity of the fuel. Depending on the determined measuredvalue the conveying output of an electric fuel pump, not illustrated, inthe low-pressure circuit of the fuel supply and/or the heating power ofthe heating element 6 can be controlled or regulated in order to ensurea satisfactory volume flow of the fuel through the fuel filter 10 evenat low temperatures of the surroundings.

The invention claimed is:
 1. A filter element of a motor vehicle fuelfilter, comprising: a filter body for installation into a filterhousing, said filter body having a raw unfiltered side and a cleanfiltered side, said filter body including; a terminal disk having athrough opening; a cylindrical filter material arranged into a pluralityof folds within said filter body; wherein two neighboring folds of saidfilter material are spread apart in a circumferential direction widerthan other pairs of neighboring folds of said plurality of folds to forman installation space between said two neighboring folds; and ablock-shaped heating element arrangeable in the filter body, the heatingelement extending substantially parallel with an axis of saidcylindrical filter media and arranged in said installation space to bespaced from and between said two neighboring folds at a radially outerside of said filter material; wherein said heating element ispositionally correlated with said through opening of said terminal disk;wherein said heating element is arranged to heat fuel in said filterbody; wherein said filter element is configured for use in said filterhousing.
 2. The filter element according to claim 1, wherein the heatingelement is arranged on the raw side of the filter body.
 3. The filterelement according to claim 2, wherein the heating element comprises adifferential pressure sensor configured to detect and responsive todifferential pressure between the raw side and the clean side of thefilter body.
 4. The filter element according to claim 3, wherein thepressure sensor is connected to control an electric fuel pump in alow-pressure circuit of the fuel supply and/or control heating powersupplied to the heating element.
 5. The filter element according toclaim 4, wherein the heating element is fixedly connected to the filterhousing and configured to enable exchange/replacement together with thefilter element.
 6. A fuel filter for motor vehicles comprising: a filterhousing including a lid part; a filter element according to claim 1received into said housing; wherein between said terminal disk and saidlid part a supply chamber is defined within said filter housing; asupply line in fluid communication with said supply chamber andconfigured to supply fuel to said supply chamber; and wherein saidthrough opening in said terminal disk adjoins said heating element. 7.The fuel filter according to claim 6, wherein in the filter element theheating element is arranged on the raw side of the filter body; whereinthe heating element comprises a differential pressure sensor configuredto detect and responsive to differential pressure between the raw sideand the clean side of the filter body; wherein the pressure sensor isconnected to control an electric fuel pump in the low-pressure circuitof the fuel supply and/or control heating power supplied to the heatingelement; and wherein the heating element is fixedly connected to thefilter housing and configured to enable exchange/replacement togetherwith the filter element.
 8. The fuel filter according to claim 6,wherein the through opening is connected to a hydrodynamic conductingbody configured to guide fuel flowing into said through opening directlyto the heating element.
 9. The fuel filter according to claim 8, furthercomprising electrical connecting contacts secured on said heatingelement and accessible through a contact opening provided in said lidpart; and a seal sealing between said lid part and said heating elementconfigured to isolate said contacts from fuel flow.